Mounting tires slightly out of spec, yay or nay?

[mareakin]

Tires manufacturers specify a range of wheel widths for their tires, for example a 175/65R15 tire specifies a wheel width range of 15x5 to 15x6 as optimal.

The question is, can you mount such a tire on a wheel that's a half inch out of spec (let's say a 15x6.5 wheel?) What about a full inch? How far can you go?

Anyone try this before? Did it feel safe?

One reason someone might try this because they may prefer a sportier ride (less sidewall flex.)

I'm thinking maybe half an inch out of spec for most tires will be OK but 1 inch would be pushing it (again this will depend on the tire size.) Do you agree?

 

[Jetronic]

Running my 205/50R17 tyres on the original 7.5" wide wheels. That's a full inch over the design width of the tyre. You are more likely to damage the wheels though, especially parallel parking...

 

[gfh77665]

Tires manufacturers specify a range of wheel widths for their tires, for example a 175/65R15 tire specifies a wheel width range of 15x5 to 15x6 as optimal.

The question is, can you mount such a tire on a wheel that's a half inch out of spec (let's say a 15x6.5 wheel?) What about a full inch? How far can you go?

Anyone try this before? Did it feel safe?

One reason someone might try this because they may prefer a sportier ride (less sidewall flex.)

I'm thinking maybe half an inch out of spec for most tires will be OK but 1 inch would be pushing it (again this will depend on the tire size.) Do you agree?

It happens a gazillion times. Unless its totally extream, you will never notice. 1" or less is NOTHING.

 

[CapriRacer]

It's called "stretching", when you go wider - and the result is a more responsive tire: less time lag to steering input. It's a trick used by autocrossers. But there is an upper limit where the bead won't stay mounted.

What else happens is the tread dearches and the tire wears in the shoulders.

Using too narrow a rim causes the tire tread to arch and ride in the center. That makes the vehicle sensitive to cross winds and ruts in the road - not to mention it wears the tire in the center.

But when using the tire within the allowable range, these things are very minimal. It's only outside that range that this becomes a problem - and the further outside, the worse the problem.

 

[lizpat]

It happens a gazillion times. Unless its totally extream, you will never notice. 1" or less is NOTHING.

It's called "stretching", when you go wider - and the result is a more responsive tire: less time lag to steering input. It's a trick used by autocrossers. But there is an upper limit where the bead won't stay mounted.

What else happens is the tread dearches and the tire wears in the shoulders.

Using too narrow a rim causes the tire tread to arch and ride in the center. That makes the vehicle sensitive to cross winds and ruts in the road - not to mention it wears the tire in the center.

But when using the tire within the allowable range, these things are very minimal. It's only outside that range that this becomes a problem - and the further outside, the worse the problem.

Running my 205/50R17 tyres on the original 7.5" wide wheels. That's a full inch over the design width of the tyre. You are more likely to damage the wheels though, especially parallel parking...

You're all basically saying the same thing: 1/2 to 1 inch is nothing, go for it!

I will! LOL.

Thanks. I'm good.

 

[CapriRacer]

No, we're not saying the same thing. I'm saying OUTSIDE the allowable range bad things start to happen - and certainly 1" is enough outside that it will be noticeable.

 

[lizpat]

No, we're not saying the same thing. I'm saying OUTSIDE the allowable range bad things start to happen - and certainly 1" is enough outside that it will be noticeable.

Oh.. thanks for the clarification. If 1" outside of spec is risky, what about .5" ----- that should be OK right? (I hope so....)

 

[Jetronic]

there's an allowable range for every tyre. For the 205/50R17 size I'm using for winter, 7.5"is the max within the allowable range, 5.5" would be the minimum, and 6.5" the design width.

 

[Pew]

To attach onto what CapriRacer said, I've ran 245-width tires on a 9.75" wheel for the track and DD and you will notice the ride being much harsher. You'll also have to run higher PSI to make up for the dearch - compounding the harsh ride and less grip when driven at the limits. The worst part is how exposed the rim of the wheel will be since there's no rubber to help protect the wheel from a deep pothole or curb.

I've also ran the opposite; 265-width tires on an 8.5 wheel for autoX and DD and it will cause a very noticeable floating feeling. I imagine this effect would be compounded on a small wheelbase car like a fiesta in the wind or highway (since the tire size you spec'd are small.)

That being said, there is one exception where a model of a tire is actually wider than other tire models of the same size although I've only notice that with sticky tires (ie: a 275 Bridgestone RE-71r was much wider than a 275 Continental ExtremeContact DW.)

 

[eljefino]

nay. a 175 on 6.5" would look and work dumb.

If you want handling, don't get a 175, lol.

 

[CapriRacer]

Just so everyone understands: There is a target value for rim width. It's called the "Measuring Rim". That's where a 245 should actually measure 248m (Long story, but believe me that NONE of the widths and aspect ratio's are exact!) - and that's what tire designers use for all their calculations.

Then there is the allowable deviation from the measuring rim width - commonly referred to as a range: Allowable rim width range. Within that range, tires perform pretty close to how they perform on the measuring rim (except for dimensions!)

Then outside that range, all bets are off - and the further away from the target value you are, the worse that is. Above we were talking about 1" outside that range, but in reality, we should have been talking about 1 1/2 " too wide!

 

[RooflessVW]

I ran 195/50R16 on 16x9 wheels back in the day.

Tires wore fine, handling was fine.

 

[benjy]

looks aside downsizing can save $$$ a weight!! for snow use a narrower tyre on a taller rim that equals OE outside diameter works well. you can find detailed specs + compare all demensions for a smart choice correct bolt patters as well as offset are required as well. my 2001 VW jetta used THREE wheel + tyre sizes 15-16-17 depending on trim lever + they were ALL very close in outside diameter for a proper fit!!